In a typical cellular radio system, wireless terminals, also known as mobile stations and/or user equipment units (UEs), communicate via a radio access network (RAN) to one or more core networks. The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” (UMTS) or “eNodeB” (LTE). A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole mobile network is also broadcasted in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units (UE) within range of the base stations.
In some versions of the radio access network, several base stations are typically connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. Specifications for the Evolved Packet System (EPS) have completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base station nodes are directly connected to the EPC core network rather than to radio network controller (RNC) nodes. In general, in E-UTRAN/LTE the functions of a radio network controller (RNC) node are distributed between the radio base stations nodes, e.g., eNodeBs in LTE, and the core network. As such, the radio access network (RAN) of an EPS system has an essentially “flat” architecture comprising radio base station nodes without reporting to radio network controller (RNC) nodes.
The Open Systems Interconnection model (OSI model) describes the functions of a communications system in terms of abstraction layers, with similar communication functions being grouped into logical layers. From top to bottom the layers are stacked this way: Application (Layer 7); Presentation (Layer 6); Session (Layer 5); Transport (Layer 4); Network (Layer 3); Data Link (Layer 2); and Physical (Layer 1).
Whenever a wireless terminal is being provided with a service, the service is associated with a radio bearer specifying the configuration for Layer-2 and Physical Layer (Layer-1) in order to have its quality of service clearly defined. Radio bearers are channels offered by Layer-2 to higher layers for the transfer of either user or control data.
When a bearer is established, a node of the radio access network determines for how long a time the bearer shall be allowed to be inactive and still hold or be allocated certain resources of the radio access network, e.g., of a base station, before the bearer is released. In other words, when not carrying data the bearer is allowed to remain in the RRC Connected Mode only for a prescribed inactivity time before the bearer is released. Typically a node such as a base station node keeps track of such inactivity time of a bearer by using an inactivity timer. In Long Term Evolution (LTE), for example, the inactivity timer is set internally in the base station node (eNb) for all bearers. That is, according to conventional practice the value of the inactivity timer is set to the same value for all user equipments, e.g., for all wireless terminals served by the node.
The choice of an inactivity timer value for a bearer has significant consequences. If the choice of inactivity timer value for a bearer is imprudent, such choice may result in misalignment between the inactivity timer setting and the service which utilizes the bearer.
For example, if the inactivity timer is given too low a value with regards to the needs of the service, the bearer will be prematurely released and thereafter it or another bearer will have to be re-established to maintain the service. Such prematurely released and re-establishment unfortunately increases the overhead signalling.
On the other hand, if the inactivity timer is given too high a value, resources will remain allocated to the bearer perhaps even long after the bearer is no longer carrying data for the service, thereby wastefully preventing other wireless terminals from using the bearer (and thus unwisely administering resources of the radio access network).
Studies regarding user behavior for interactive type services (e.g. web browsing) show that there is seldom new user activity after 60 seconds of inactivity for such services. Consequently, the inactivity timer is set to 61-64 seconds in most radio access network implementations.
However, the inventors believe that a uniform inactivity timer setting of about 61 seconds is not optimal for other types of services. For example, considering short message service (SMS), when an SMS is delivered to the UE relevant bearers are created to the UE and the SMS is delivered. Even if the SMS is delivered very quickly (less than a second) the bearers will remain until they time out. So for one way SMS delivery it might be preferable to have very a very short inactivity timer value. But if the user is supposed to answer the SMS, the connection must be kept alive until the response is completed. These same types of considerations are also valid for other kinds of IP traffic, e.g. MSN/Yahoo Messenger messages, applications that check for weather once every 30 minutes, etc.
Another area where uniform inactivity timer setting may be a problem is machine-to-machine communication where certain kinds of connections may require a client to send a burst of data followed by a potential acknowledgement. In such machine-to-machine communication the inactivity timer could have a very low value relative to web browsing services or the like.
Thus, a problem arises in that different types of services could require different type (e.g., different length) of inactivity timer settings for their respective bearers.